Automatic choke



Aug. 2, 1966 F. J. MARSEE AUTOMATIC CHOKE Filed 001:. '7, 1964 2Sheets-Sheet l F/PED'P/CK JI MARJEE IN V EN TOR.

BY fig W g 2, 1 F. J- MARSEE 3,263,661

' AUTOMATIC CHOKE Oct. 7, 2 sheets-sheet 2 FREDERICK J MA/PJEE IN VENTOR.

United States Patent 3,263,661 AUTOMATIC CHOKE Frederick J. Marsee,Hazel Park, Mich, assignor to Holley Carburetor Company, Warren, Mich.,a corporation of Michigan Filed Oct. 7, 1964, Ser. No. 402,093 13Claims. (Cl. 123-119) This invention relates generally to carburetorsfor internal combustion engines, and more particularly to a novelautomatic choke control mechanism therefor.

Carburetor automatic choke control mechanisms in which the chokeposition is influenced by engine temperature and vacuum have been knownand used for many years. Such a mechanism is shown by Smitley, U.S.Patent No. 2,988,344.

While these prior art systems have been commercially successful, theyinvolve a substantial number of individual parts, the result being thatthe assembly is expensive to manufacture.

Many prior art carburetors include a lower throttle body casting and anupper main body casting to which the fuel bowl and the automatic chokemechanism are connected. The two castings are separated by a gasketwhich tends to prevent the conduction of engine heat to the uppercasting. While it is desirable to keep heat away from the fuel bowl,this reduction in radiated and conducted engine heat to the automaticchoke mechanism makes the thermostatic element of the choke mechanismless responsive to engine heat. For example, it will coo-1 off fasterthan the engine when the engine is shut down; thus, the choke willprematurely return to a closed position, as in the case of a relativelyshort engine shut down, and make restarting diflicult.

Another inherent disadvantage of the choke mechanism shown by Smitley isthat the linkage between the thermostatic coil and the choke plate issuch that the torque output of the thermostatic coil is substantiallyconstant. This makes it more difiicult or impossible to make small chokeadjustments for different engine applications.

The tendency today is toward reduction in cost of manufacture andstandardization. Accordingly, a primary object of this invention is toprovide an automatic choke control mechanism of the type shown bySmitley, but wherein the number and complexity of the individual partsis substantially reduced as to reduce the over-all cost of themechanism.

Another object of the invention is to provide a choke control mechanismthat forms a part of the throttle body casting so as to be moreeffectively subjected to conducted andradiated engine heat, which is thedesired parameter.

Still another object of the invention is to provide such a mechanismwherein the torque output characteristics of the thermostatic coil canbe changed, within limits, so

. as to enable minor adjustments and thus permit a single thermostaticcoil to serve more engine applications, or special applications.

These and other objects and advantages of the invention will become moreapparent upon reference to the following specification and theaccompanying drawings wherein:

FIGURE 1 is a side el-evational view, with portions thereof cut away andin cross section, illustrating a carburetor having an automatic chokecontrol mechanism embodying the invention.

FIGURE 2 is a fragmentary top plan view of the carburetor shown byFIGURE 1, with the cover of the choke control mechanism cut away tobetter illustrate the internal structure.

FIGURE 3 is a view similar to FIGURE -1, but taken substantially on theplane of line 3-3 of FIGURE 2 to illustrate additional details ofconstruction.

Referring now to the drawings in greater detail, FIG- URE 1 illustratesa carburetor 10 embodying the invention, mounted on an intake manifold12 of an internal combustion engine. In this particular instance, thecarburetor 10 generally comprises three cast sections, including anupper so-calle-d air horn casting 14, an intermediate main body casting16 and a lower throttle body casting 18. As usual, the assembledcarburetor includes an in duction passage 20 having a venturi 22. Theusual offset choke plate 24 is secured on a shaft 26 pivotally mountedin the induction passage 20 upstream of the venturi 22, and the usualthrottle plate 28 is likewise secured to .a shaft 30 pivotally mountedacross the induction passage downstream of the venturi 22. Thecarburetor also includes a fuel reservoir 32 formed with theintermediate main body section 16, and the carburetor sections aresecured together in any suitable manner such as by means of the screws34, with gaskets 36 positioned between the sections to prevent leakage.

The operation of the throttle plate 28, which is spring loadedto close,through the foot throttle valve is well known in the art. Since it formsno part of this invention, this structure is not shown.

A preferably elongated, generally hollow housing 38 containing theimproved choke control mechanism, designated generally as 40, may beformed integral with the throttle body casting 18, or it may be attachedthereto. In the carburetor shown, the housing 38 is cast integrally withthe throttle body, and a stamped cover member 42 is provided to enclosethe mechanism, the cover being secured by any suitable means such as thescrews 44 and sealed by gaskets 45 and 47.

The shaft 26 to which the choke plate 24 is fixed extends through thewall of the carburetor and has secured thereto a lever 46. A link 48 ispivotally secured at the upper end thereof to the lever 46 by means of aclip 50, the other end of the link 48 extending downwardly into- -thehousing 38, through an eyelet 41 in the cover 42, so as to have thelower transverse end 52 thereof in a position to be engaged by the outerradially extending free end 54 of a thermostatic bimetal coil element56. The inner end of the coil 56 is fixedly secured in the usual mannerthrough the slot 58 in the shaft 60, the rotational position of whichmay be set to determine the preload of coil 56 by engagement of thetoothed wheel 62 secured to the shaft with a pointed lug 64 formed onthe housing 38. Alternatively, the Wheel 62 may be replaced by a slottedplate adapted to receive a screw to hold the plate in any desiredposition. Bearing openings in the cover 42 locate the shaft 60. i

As is well known in the art, the thermostatic coil 56 is formed so as toexpand with decreasing temperature and to contract with increasingtemperature. Thus, at lower temperatures, the coil tends to unwind sothat the free end 54 thereof tends to close the choke valve 24 throughits engagement with the link 48. As alreadly stated, the choke closingforce of the thermostatic coil 56 can be varied by adjusting the initialrotational position of the shaft 60.

The housing 38 is preferably formed at the other end thereof with avertically positioned cylinder 66, the closed end of which is incommunication with engine manifold vacuum by means of the passage 68extending from the induction passage 20 at a point downstream of thethrottle plate 28 and communicating with the bottom of the cylinderthrough the opening 70. The cylinder walls are formed at the upper endthereof with a pair of aligned slots 72 adapted to receive the free endof a wire or other suitably formed beam member 74, the other end 76 ofwhich is rotatably anchored, as by a loop, to the shaft 60 on which theinner end of the thermostatic coil is fixedly mounted. As will beexplained, the beam 74 may be rigid, or it may flex at a predeterminedrate.

A piston 78 is positioned in the cylinder 66, the piston preferablyhaving only suificient clearance to allow engine vacuum to cause air toflow by the piston and yet to cause the piston 78 to move downwardly inthe cylinder in response to the same engine vacuum. The upper portion ofthe piston is formed to provide an annular groove 80 aligned with thegrooves 72 formed in the cylinder wall so that beam 74 member may bereceived both in the annular groove 80 in the piston and the verticalgrooves 72 in the cylinder wall. It will also be noted that the beam '74passes above the transverse end 52 of the link 48 that engages the freeend 54 of the thermostatic coil 56.

Other details of construction of the housing 38 to be noted are the airinlet 82 and the bafile 84 having an opening 86, the bafile causing air,preferably coming from the air cleaner 88 and heated stove 90 positionedin or near the exhaust manifold 92 in the usual manner well known in theart, to pass both over and under the thermostatic coil 56 to heat thesame more uniformly. The heated air eventually passes into the open topof the cylinder 66, around the piston 78 and thence into the intakemanifold by way of a passage 68, as indicated by the arrows.

The sides of the housing 38 are formed with suitable projections 94 and96 providing oppositely disposed aligned slots 98 to receive the shaft60 and a second pair of slots 100, the outermost of which is adapted toguide the lower transverse end 52 of the link 48. It is understood thatthe slots 98 may be initially formed to provide either a deeper or ashallower seat for the shaft 60, as indicated by the dotted lines A andB in FIGURE 1. Since the link 48 must move through the fixed opening 41in the cover member 42, the outer slot is formed with an angular camportion 102 to guide the lower end of the link in a manner to permit theupper end of the link to move outwardly, as it must due to the arcuatemovement thereof resulting from its pivotal connection to the chokelever 46, as shown in dotted lines in FIGURE 1. It will thus be notedthat while the upper end of the link moves at a fixed radius, the lowerend of the link does not move at a fixed radius.

The extent to which the piston 78 can move downwardly in response toengine vacuum may be manually adjusted by means of the screw 104 havinga cone end. Alternatively, the piston itself can be formed so as toenable variation in its travel.

As best seen in FIGURES 2 and 3, a fast idle and dechoke lever 106 ispivotally secured at one end thereof to the fuel bowl portion of thecarburetor by means of a washer 108 and screw 110. Lateral movement ofthe lever is prevented by means of the bosses 112 extending from thefuel bowl, movement of the lever being thus limited to pivotal movementabout the screw 110 in the plane of the lever.

It will be noted that the link 48 has a transverse portion 114intermediate the ends thereof at a point above the cover 42. An upperarm 116 of the lever 106 extends over this transverse portion 114 and ispositioned thereby. In other words, the lever 106 is free to pivot andwill always fall in a counterclockwise direction about the screw untilit engages the transverse portion 114. It is apparent that movement ofthe choke plate 24 to the closed position, as shown in dotted lines,will raise the link 48, and at the same time pivot the lever 106clockwise.

The intermediate left-hand portion of the lever 106 is formed with aseries of steps 118, 120 and 122 which comprise a fast idle mechanismco-operating with the free, laterally extending end 124 of the lever 126secured to pivotwith the end of the throttle shaft 30 protruding throughthe wall of the carburetor. Since the throttle 28 is spring loaded toclose, the tap 124 on the lever 126 will either be free of or engage oneof the steps 118, and 122, depending upon the choke position when thethrottle is released. The tap 124 may be formed with an opening adaptedto receive a tool, such as a screwdriver, with which the tab may besuitably bent to provide fast idle settings intermediate that providedby the steps, correct for misalignment, etc.

The lower left-hand arm 128 of the lever 106 is formed with a portion130 turned into the carburetor so as to be engaged by the intermediatecontoured portion of the lever 126 so as to cam the lever 106counterclockwise andopen the choke when the throttle is opened fully.

Operation When an engine is shut down after a run, the engine is atnormal operating temperature and the choke 24 is open, as shown in solidlies in FIGURE 1. The fast idle lever 106 would thus be in its mostcounterclockwise position, and the lever 126 would have been positionedabove the first step 118. The thermostatic coil 56 would be wound up soas to be positioned below and away from the bottom transverse end 52 ofthe link 48.

As the engine cools, the thermostatic coil 56 cools so as to unwinduntil it engages the bottom transverse end 52 of the link 48, thereafterurging the link upwardly and the choke closed. However, the first step118 coming into engagement with the tap 124 on the lever 126 preventsthe lever 106 from pivoting clockwise and the choke from closing. Sincethere is no engine vacuum, the piston78 is free, and it falls to thebottom of the cylinder, the beam 74 being pivotally connected to theshaft 60.

The first step in starting a cold engine is to depress the footthrottle. This opens the throttle 28 and causes the lever 126 to movecounterclockwise in FIGURE 3, disengaging the tap 124 from the firststep 118 and allowing the stressed coil 56 to unwind and raise the link48, thereby closing the choke valve 24. The lower transverse end 52 ofthe link will also raise the beam 74, and thus the piston 78, to itsuppermost position. At the same time, link 48 will rotate lever 106clockwise so that the tab 124 will engage the fast idle step 122 whenthe throttle is released.

The ignition key is then turned on and the engine is cranked. As soon asthe engine starts and becomes selfsustaining, and while the coil isstill in the cold condition and tending to close the choke 24, thepiston 78 will be drawn downwardly by engine vacuum to the stop 104,causing the beam 74 to move the link 48 downwardly and partially openingthe choke plate, against the closing force of the still cold unwoundthermostatic coil.

Once the piston 78 reaches the stop 104, further choke opening due toair flow on the unbalanced choke plate 24 is resisted only by the forceof the coil 56. As warm air is drawn through the housing and around thethermostatic coil, the coil is progressively heated, causing it to windup and offer less and less resistance to choke sirable to provide achoke control mechanism in which the characteristics of the bimetalmovement may be readily changed.

Since the lower end of the link 48 does not traverse afixed radius, asopposed to the typical prior art structure of Smitley, a maximummechanical advantage occurs at some given point, which can be adjustedby simply repositioning the bimetal post or shaft 60 vertically, eitherup or down from the position shown in FIGURE 1.

Such a shift in shaft position will also adjust the torquecharacteristics, within a limited range of choke plate travel, and canbe accomplished by changing the depth of the slots 98, as already statedabove.

With the proposed choke mechanism, the above changes or adjustments inchoking characteristics can be easily made, without resorting tocomplicated lever modifications, as would be required in the case of theSmitley structure wherein the choke link does traverse a constantradius.

It will also be noted that the beam 74, which is pulled downwardly bythe piston so as to move the link 48 downwardly and open the choke plateagainst the force of the thermostatic element, may be of a wire springconstruction. It is apparent, if the bending movement of the beam islower than the force of the thermostatic element, that under certainpredetermined temperature conditions the beam will be forced to bend apredetermined amount. This bend of the beam will prevent the choke platefrom being opened to the same angle, for a constant piston travel, as itwould be if the beam were rigid. Thus, the fuel-air mixture can bemodulated in accordance with temperature changes.

By actual count, the number of separate pieces required for a completeSmitley type choke system is approximately 39; with the proposedstructure, the number of pieces required for a complete choke system isreduced to approximately 28.

Furthermore, since the housing containing the thermostatic element islocated at the lower portion of the carburetor near the engine,'it ismore responsive to conducted and radiated engine heat, which is thedesired parameter. Also, such a location reduces the length and exposureof the passage required to connect the vacuum cylinder with manifoldvacuum and the housing with the stove.

It should be apparent that various modifications may be possible withinthe scope of the appended claims.

What I claim as my invention is:

1. In an internal combustion engine carburetor automatic choke mechanismof the type wherein a thermostatic force opposes a choke plate unbalanceforce substantially at all times during engine operation and an enginevacuum force overcomes the thermostatic force when the engine firststarts, a member pivotally connected at one end thereof to said chokeplate and means whereby said thermostatic and engine vacuum forces areapplied to said member from opposite sides thereof, said structure beingfree of any pivotal connections at the point of application of saidforces.

2. In an internal combustion engine carburetor automatic choke mechanismof the type wherein a thermostatic force opposes a choke plate unbalanceforce substantially at all times during engine operation and an enginevacuum force overcomes the thermostatic force when the engine firststarts, a link pivotally connected at one end thereof to said chokeplate and means whereby said thermostatic and engine vacuum forces areapplied in opposite directions directly to the other end of said link.

3. In a carburetor automatic choke mechanism of the type wherein theopening of a choke plate olfset to open in response to flow of air tothe engine is opposed by a thermostatic coil element anchored atitsinner end and responsive to engine heat so that opposition to chokeopening decreases with increasing engine temperature and assisted by apressure responsive member actuated fully by any engine vacuum exceedingengine cranking vacuum, means for connecting said choke plate, saidthermostat and said vacuum responsive member, said means comprising alink pivotally connected to an arm extending from said choke plate, thefree end of said link having a lateral extension passing betweenelements extending from said coil and said pressure responsive member soas to be acted upon by said elements from opposite sides thereof and sothat the torque output characteristics of said coil may be varied byvarying the location of said coil anchor.

4. A carburetor for an internal combustion engine, comprising a bodyformed with (1) an induction passage having a venturi restriction, (2) achoke plate mounted on a pivotable shaft and positioned upstream of saidventuri, (3) a throttle plate mounted on a pivotable shaft andpositioned downstream of said venturi, and (4) an automatic chokecontrol mechanism, said mechanism including (a) a housing extending fromsaid body adjacent one end of said throttle shaft;

(b) a cylinder formed at one end of said housing, said cylinder having aslot formed lengthwise through the wall thereof;

(0) a piston in said cylinder, said piston having an annular grooveformed in the outer surface thereof;

(d) adjustable means for limiting the travel of said piston;

(e) a passage communicating between the induction passage downstream ofsaid throttle plate and a source of air heated by said engine, saidpassage including said cylinder and said housing;

(f) a thermostatic element positioned in said housing, said thermostaticelement comprising a bimetallic coil spring having the inner end thereofsecured to a rotatably adjustable shaft extending across said housingand the outer free end thereof formed to provide a radially extendingabutment;

(g) a lever secured to said choke shaft;

(h) a link pivotably mounted at one end thereof to said lever andextending into said housing through the top wall thereof, said linkhaving a transverse portion intermediate the ends thereof, the free endof said link within said housing having a lateral extension engagingsaid abutment formed on the free end of said thermo static element sothat said element tends to close said choke plate through said link whenit is cold; and

(i) a beam having one end thereof pivotally secured on said shaft towhich said inner end of said thermostatic element is secured, said beamextending across said lateral extension of said link toward saidcylinder and the free end thereof being positioned both in said slot insaid cylinder and in said groove in said piston, said beam being inengagement with said lateral extension when said choke is closed so asto open said choke against the force of said thermostatic element whensaid piston is moved downwardly to its stop due to engine vacuum whenthe engine is started.

5. In a carburetor for an internal combustion engine including a bodyformed with (1) an induction passage having a venturi restriction,

(2) a choke plate mounted on a pivotable shaft and positioned upstreamof said venturi,

(3) a throttle plate mounted on a pivotable shaft and positioneddownstream of said venturi, and

(4) an automatic choke control mechanism, said mechanism comprising (a)a housing extending from said body adjacent one end of said throttleshaft;

(b) a cylinder formed at one end of said housing, said cylinder having aslot for-med lengthwise through the wall thereof;

(0) a piston in said cylinder, said piston having an annular grooveformed in the outer surface thereof;

(d) adjustable means for limiting the travel of said piston;

(e) a passage communicating between the induction passage downstream ofsaid throttle plate and a source of air heated by said engine, saidpassage including said cylinder and said houss;

(f) a thermostatic element positioned in said housing, said thermostaticelement comprising a bimetallic coil spring having the inner end thereofsecured to a rotatably adjustable shaft extending across said housingand the outer free end thereof formed to provide a radially extendingabutment;

(g) a lever secured to said choke shaft;

(h) a link pivotably mounted at one end thereof to said lever andextending into said housing through the top Wall thereof, said linkhaving a transverse portion intermediate the ends thereof, the free endof said link within said housing having a lateral extension engagingsaid abutment formed on the free end of said thermostatic element sothat said element tends to close said choke plate through said link whenit is cold; and

(i) a beam having one end thereof pivotally secured on said shaft towhich said inner end of said thermostatic element is secured, said beamextending across said lateral extension of said link toward saidcylinder and the free end thereof being positioned both in said slot insaid cylinder and in said groove in said piston, said beam being inengagement with said lateral extension when said choke is closed so asto open said choke against the force of said thermostatic element whensaid piston is moved downwardly to its stop due to engine vacuum whenthe engine is started.

6. In a carburetor for an internal combustion engine including a bodyformed with (1) an induction passage having a venturi restriction,

(2) a choke plate mounted on a pivotable shaft and positioned upstreamof said venturi,

(3) a throttle plate mounted on a pivotable shaft and positioneddownstream of said venturi, and

(4) an automatic choke control mechanism, said mechanism comprising (a)a substantially sealed housing;

(b) a cylinder formed in said housing, said cylinder having a slotformed lengthwise through the wall thereof;

(c) a piston in said cylinder, said piston having an annular abutmentformed on the outer surface thereof;

(d) a passage communicating between the induction passage downstream ofsaid throttle plate and a source of air heated by said engine, saidpassage including said cylinder and said hous- (e) a thermostaticelement positioned in said housing, said thermostatic element having oneend thereof adjustably secured to said housing and the other free endthereof extending toward said cylinder;

(f) an arm extending from said choke shaft;

(g) a link pivotably mounted at one end thereof to said arm andextending into said housing through a wall thereof, said link having atransverse portion intermediate the ends thereof and the free end ofsaid link within said housing having a lateral extension engaging saidfree end of said thermostatic element so that said element tends toclose said choke plate through said link when it is cold; and

.(h),a beam having one end thereof pivotally secured to said housing,said beam extending across said lateral extension of said link towardsaid cylinder and the free end thereof being engaged in said slot insaid cylinder and adjacent said abutment on said piston, said beam beingin engagement with said lateral extension when said choke is closed soas to open said choke against the force of said thermostatic elementwhen said piston is moved downwardly due to engine vacuum when theengine is started.

7. In a carburetor automatic choke mechanism of the type wherein theopening of a choke plate offset to open in response to flow of air tothe engine is opposed by a thermostatic coil element anchored at itsinner end and responsive to engine heat so that opposition to chokeopening decreases with increasing engine temperature and assisted by apressure responsive member actuated fully by any engine vacuum exceedingengine cranking vacuum, means for connecting said choke plate, saidthermostat and said vacuum responsive member, said means comprising alink pivotally connected to an arm extending from said choke plate, thefree end of said link having a lateral extension passing betweenelements extending from said coil and said pressure responsive member soas to be acted upon by said elements from opposite sides thereof, saidelement extending from said pressure responsive member having apredetermined bending moment so as to provide modulation of the effectof said thermostat.

8. In a carburetor automatic choke mechanism of the type wherein theopening of a choke plate offset to open in response to flow of air tothe engine is opposed by a thermostatic coil element anchored at itsinner end and responsive to engine heat so that opposition to chokeopening decreases with increasing engine temperature and assisted by apressure responsive member actuated fully by any engine vacuum exceedingengine cranking vacuum, means for connecting said choke plate, saidthermostat and said vacuum responsive member, said means comprising alink pivotally connected to an arm extending from said choke plate, thefree end of said link having a lateral extension passing betweenelements extending from said coil and said pressure responsive member soas to be acted upon by said elements from opposite sides thereof, and sothat the torque output characteristics of said coil may be varied byvarying the location of said coil anchor, said element extending fromsaid pressure responsive member having a predetermined bending moment soas to provide modulation of the effect of said thermostat.

9. In a carburetor automatic choke mechanism of the type wherein theopening of a choke plate offset to open in response to flow of air tothe engine is opposed by a thermostatic coil element anchored at itsinner end and responsive to engine heat so that its opposition to chokeopening decreases with increasing engine temperature and assisted by apressure responsive member actuated fully by any engine vacuum exceedingengine cranking vacuum, means for connecting said choke plate, saidthermostat and said vacuum responsive member, said means comprising alink pivotally connected to an arm extending from said choke plate, thefree end of said link having a lateral extension merely passing betweenand being free of positive connections to elements extending from saidcoil and said pressure responsive member.

10. In a carburetor automatic choke mechanism of the type wherein theopening of the choke plate is opposed by a thermostatic elementresponsive to engine heat and assisted by a pressure responsive memberactuated by engine vacuum, means for connecting said choke plate, saidthermostat and said vacuum responsive member, said means comprising alink pivotally connected at one end thereof to an arm extending fromsaid choke plate, said link being arranged so that said pivoted end ofsaid link traverses a constant radius arc, the other free end of saidlink traversing a different path so as to have a distinct maximummechanical advantage at some particular point,

said point being variable by varying the direction of forces actingthereon.

11. In a carburetor automatic choke mechanism of the type wherein theopening of the choke plate is opposed by a thermostatic elementresponsive to engine heat and assisted by a pressure responsive memberactuated by engine vacuum, means for connecting said choke plate, saidthermostat and said vacuum responsive member, said means comprising alink pivotally connected at one end thereof to an arm extending fromsaidchoke plate, said link being arranged so that said pivoted end of saidlink traverses a constant radius arc, the other free endof said linktraversing a ditferent path so as to have a distinct maximum mechanicaladvantage at some particular point.

12. An internal combustion engine carburetor automatic choke mechanismcomprising an offset choke plate, a thermostat heated by the engine, anda link extending between said choke plate and said thermostat so thatopening of said choke plate is resisted by the force of said thermostat,said link being arranged so that its maximum mechanical advantage occursat a single fixed point, whereby said point can be varied merely byvarying the direction of application of said thermostat force.

13. An internal combustion engine carburetor automatic choke mechanismcomprising an offset choke plate, a thermostat heated by the engine, alink extending between said choke plate and said thermostat so thatopening of said choke plate is resisted by the force of said thermostat,said link being arranged so that its maximum mechanical advantage occursat a single fixed point, whereby said point can be varied merely byvarying the direction of application of said thermostat force, an enginevacuum responsive device assisting initial opening of said choke plate,and means to modulate the effect of said thermostat.

References Cited by the Examiner UNITED STATES PATENTS 2,862,488 12/1958Nastas 123-119 2,956,558 10/1960 Sterner 123-119 2,957,465 10/1960Wagner 123-119 2,962,014 11/1960 Durler 123-119 2,988,344 6/ 1961Smitley 261-39 MARK M. NEWMAN, Primary Examiner. KARL J. ALBRECHT,Examiner.

1. IN AN INTERNAL COMBUSTION ENGINE CARBURETOR AUTOMATIC CHOKE MECHANISMOF THE TYPE WHEREIN A THERMOSTATIC FORCE OPPOSES A CHOKE PLATE UNBALANCEFORCE SUBSTANTIALLY AT ALL TIMES DURING ENGINE OPERATION AND AN ENGINEVACUUM FORCE OVERCOMES THE THERMOSTATIC FORCE WHEN THE ENGINE FIRSTSTARTS, A MEMBER PIVOTALLY CONNECTED AT ONE END THEREOF TO SAID CHOKEPLATE AND MEANS WHEREBY SAID THERMOSTATIC AND ENGINE VACUUM FORCES AREAPPLIED TO SAID MEMBER FROM OPPOSITE SIDES THEREOF, SAID STRUCTURE BEINGFREE OF ANY PIVOTAL CONNECTIONS AT THE POINT OF APPLICATION OF SAIDFORCES.